Gravity separation of ores



Sept. 29, 1942. H. H. WADE 22,191

GRAVITY SEPARATION OF ORES Original Filed March 31, 1938 2 Sheets-Sheetl f/ecfro Mayne/.5- k

Magnef/c f0 "4752? l 9 "fisher j n c d I I ru 6 Ore 5/ Conveyo 's/7IVdfer Fefurh ven/ba Sept. 29, 1942. H. H. WADE GRAVITY SEPARATION OFORES Original Filed March 31. 1958 2 Sheets-Sheet 2 Invenior 1 n A2 1rryys Reissued Sept. 29, 1942 ram oaavrrr snraaarron or ones Henry H.

mesne Wade, Hopkins, Ilium, assignor, by assignments, to MineralsBeneficiatlon,

Incorporated, a corporation of Delaware Original No. 2,206,980, datedJuly 9, 1940, Serial No. 189,197, March 31, 1938. Application Iorreissue June 25, 1941, Serial No. 399,718

1: Claims. 01. a ts-so) This invention relates to the gravity separationof the heavier ores from their impurities or tailings in a fluid massconsisting of liquid, preferably water, and solids insoluble in theliquid and of such character and fineness that by slight agitation ofthe mixture a uniform mass having a specific gravity within the range of2.5 to 3.3 may be maintained.

Heretofore, the solid, insoluble constituents of the flotation mediumsused in methods [or concentrating ores, such as iron, manganiferousiron, copper, lead and zinc ores, by gravity, have not been satisfactorybecause of the difficulty of sep-- arating the mediums from the oreconcentrate and the resulting contamination of the concentrates by theintroduction of objectionable impurities such as lead and sulphur orcompounds of either or both these objectionable constituents oi themedium. The crude ores referred to have such a high specific gravitythat in order to float the rock, sand and other tailings in a body offluid medium the medium must have a specific gravity in some cases inexcess of 2.5 and in order to obtain a fluid mass of the requireddensity and at the same time provide the necessary fluidity it isessential that the solid constituent of the medium have a specificgravity in excess of 6.

By the present invention crude ores having a specific gravity in excessof 2.5 may be concentrated in a novel fluid mass containing comminutedsolids of magnetic susceptibility which solids are then separated fromthe ore concentrates and tailings by magnetic attraction.

The invention further provides a continuous novel process formaintaining a predetermined speciflc gravity in such a flotation mediumand repeatedly utilizing substantially all of the solid constituents ofthe medium while separating the medium from both the tailings andconcentrates and delivering the latter substantially free of the medium.

As the preferred solid constituent of the medium, I employ term-silicon,reduced to minus 65 to 100 mesh, and containing in excess of 75% byweight of iron. For the concentration of certain iron ores, a.ferro-silicon containing about 82% iron, 13% to 14% silicon and a smallamount oi carbon has been used successfully. Such ferrosilicon ispreferably ground to minus 100 mesh and a medium is formed therefrom bymixing the line ferro-silicon with about 25% of its weight of water.Such ierro-silicon is highly rust resistant, is recoverable irom thetailings and concentrates by magnetic attraction and has the furtheradvantage" of being so hard that it may be used repeatedly withoutdeterioration. It has a hardness of about '1, Moh's scale, and itsspecific gravity is about 7.5. As a substitute tor the ferro-silicon,high carbon steel may be used having an iron constituent in excess of byweight. High carbon steel in finely divided form makes a good medium butnormally is not so rust resistant as ferro-silicon and hence is subjectto higher losses due to oxidation in the liquid medium.

My preferred procedure for utilizing such metallic mediums in theconcentration of ores will be best understood by reference to theaccompanying drawings in which:

Figure 1 is a diagrammatic illustration of suitable apparatus andconnections for carrying out the process.

Fig. 2 is a somewhat enlarged central vertical section through thepreferred form 0! concentration tank;

Fig. 3 is a plan view of the lower part ofthe concentrating chamber, and

Fig. 4 is a plan view of the head box for distributing the medium to thetank.

Referring to Fig. 1, the numeral 5 indicates a bin or hopper for thecrude ore which in the case of iron ore is preferably reduced to aboutone inch mesh and is continuously led from the hopper to a conveyor 8,operating continuously, to deliver a stream of the ore intoa'i'unnel-like receptacle 1. From this receptacle the ore passes bygravity through a pipe l into the upper part of a concentrating tankindicated generally by the numeral 0. The lower portion III of this tankhas the form of an inverted cone and has a central opening in its bottomto deliver the settled ore concentrate into a pipe II. 'The u perportion I! of tank l is also conical but converges upwardly to arestricted top opening, its upper periphery I3 extending horizontally todeliver the floated tailings and a portion of the fluid medium into anannular launder It. This launder delivers the overflow to the upper endof an inclined screen ll, preferably 01' the punch plate type having amultiplicity of openings about two millimeters in diameter. The tailingsare retained on the screen while the bulk of the liquid and solidconstituents of the medium pass through it into a catch basin ll mountedbeneath the screen near its upper end. The tailings with adheringparticles of medium and of fine tailings, continue down the screen ii.Suitable means for jigging the screen i 5 may be provided to augment thegravitational movement of the tailings down along this screen, inaccordance with the common practice in this art. While in motion downthe lower portion of the screen, the tailings 'are subjected to watersprays issuing from the pipes II. This spray washes oil the adheringparticles of medium and flne tailings into a catch basin II and thewashed tailings are discharged from the lower end of the screen I.

A liquid flotation medium, preierablyconsisting oi 80% by weight orflnely divided terrosilicon and about 20% by weight of water isdelivered into ahead box I! and thence passes througha series ofsupplypipes 20 communicating with the tank 9 at a number of pointsuniiormly distributed around the periphery of the tank and at asubstantial distance below the upper periphery l3 thereof. This medium,which has a specific gravity of about 3, fills the tank 9 and iscontinuously supplied in sumcient volume and at such velocity as tomaintain the solid constituent thereof in suspension. A portion of themedium overflows the periphery l3 of the tank 9 and carries with it thetailings consisting largely of rock and sand. Medium also flows downthrough. the lower portion IQ of the concentrating tank and out throughthe pipe II with the oreconcentrates which have settled out due to theirhigher specific gravity than either the medium or tailings. The greaterpart 01' the overflow fluid medium passes through the screen It into thebasin Ii from which it is delivered into a pipe 2| arranged to supply anair lift22. Air under pressure is injected into the lift 22 through apipe 23 and carries the liquid medium up through a pipe 24 which returnsthe medium to the head box l9.

The concentrates and some medium are discharged from the bottom of thetank 9 through the pipe II and are carried by an air lift 25 and pipe 25to the upper end oi a screen 21. This screen is like the screen II andcarries the ore concentrate in a thin layer or st eam to the lower endof the screen from which the ore falls into a suitable receptacle orpile. The bulk of the medium, after flowing from the pipe 26, passesthrough the screen into a basin 23 and thence through a pipe 29, airlift 30 and pipe 3| back into the head box l9. As the ore concentratepasses down the screen 21, it is subjected to a water spray from pipes32, which spray removes the adhering particles of medium and fines fromthe concentrates and washes them into a basin 33 extending beneath thescreen.

The wash water,'carrying the tailing flnes, some ferro-silicon andconcentrate flnes is discharged from the basins l8 and 33 into pipes 34and 35 respectively extending to a suitable pump 36. This pumpdischarges the fluid mixture through a pipe 31 into a receptacle 38which distributes the liquid and lines in a thin stream over a plate 39.Moving adjacent to the plate 39 is a belt 40 having electro-magnets 4|above it. These magnets are supplied with direct current and the belt iscontinuously driven in the direction indicated by arrows. The belt 40moving in the field or the magnets 4|, passes closely adjacent to thestream flowing over the plate 39 and picks up, by magnetic attraction,on its bottom surface substantially all of the ferrosilicon while theparticles of tailings, being nonmagnetic, are not lifted by magneticattraction, but tall from the end of the plate 33, together with thegreater part of the water constituent into waste hoppers 42. From thesehoppers the etic particles and water are discharged through pipes. nebelt 40 carries the adhering particles of ierro-silicon to a pointsomewhat beyond the influence of the electro-magnets 4| at which pointsuch particles are released from the belt and fall into a hopper 44, inwhich the water is largely'free. from waste products. From this hopperthe medium passes through a pipe 45 into a settling tank 46 containingwater in a sufliciently quiescent state to permit the metallic solids tosettle to the bottom. As these solids remain in their polarizedcondition, the smaller particles adhere to the larger ones and thesettling is accelerated due to the resulting adherence of the particlesto each other, until the subsequent demagnetizing treatment. The solidsare thus concentrated in the water in tank 48 to secure a medium of therequired speciflc gravity and the medium is then removed from the bottomor the tank 46 by an outlet pipe 41. During removal of the medium fromthe tank 46, rake arms 48 are slowly rotated by power applied to asupporting shai't 49. The pipe 41 carries the concentrated medium,having a specific gravity in excess of 2.5 axially through ade-magnetizer 50, which is supplied with alternating current. Theresidual magnetism of the particles is thus destroyed so that they maybe readily diffused in the fluid mass. The pipe 41 then returns thedemagnetized concentrated medium to the head box I9.

Water is displaced from the top of the tank 49 and may be collected in alaunder 5| together with such small amounts oi the magnetic solids asare carried over by the water. launder discharges through a pipe 52 intoa mag neticlog washer 53 which separates the magnetic solids from thebulk of the water. The magnetic solids are discharged from this washerthrough a demagnetizer 54 and are returned to the head box is through apipe 55 and th pipe 24. The use of the magnetic log washer 53 isoptional and in some cases it may be practical to merely waste theoverflow from the settime tank 46.

As shown in Figs. 2 and 4, the lower portion of the head box I9 isdivided by partitions 55 into separate outlet chambers. of thepartitions 55 extend in a common horizontal plane and the several pipes20 communicate respectively with several outlet chambers thus tor-med.The upper surface of the medium in the'box i9 is maintained above theupper edges of the partitions 56 so that the several pipes 20 areuniformly supplied with medium.

To prevent thebuilding up of the ore con-' centrate on the conical wallsof the lower portion ill or the tank 9, rake arms 51 are arranged toextend parallel to elements of the conical surface and are slowlyrotated within the tank. The upper ends of the several arms 51 arerigidly secured to a ring 58 and this ring has arms 5!! connecting it toa central shaft 60 which projects from the top of the tank 9 and isarranged to be rotated by suitable mechanism, such as the gearingindicated at 6| (Fig. 2).

It is not essential that the crude ore be crushed to about one inchsize, as hereinbefore described and crushing to much larger or smallersizes is frequently desirabl although the equipment must be designed tohandle the particular size selected. In the recovery of the solid fromthe wash water it is sometimes desirable to pass the fluid from the pipe31 through a thickener or dewatering equipment of suitable design beforeThis The upper edges,

conducting the solids to the receptacle ll. Thickening or dewateringtreatment of the overflow from the tank 40 may also be applied to thefluid feed for the magnetic leg washer 51.

It will now be evident that the process herein described is a continuousone in which the ore concentrates, substantially free from the flotationmedium, are discharged from the screen 21 while the tailings, washedtree of the medium, are discharged from the screen ll. The solidconstituents of the flotation medium are recovered magnetically andcontinuously, substantially l'ree of impurities and returned, afterbeing demagnetized, to the gravity separation tank.

The ierro-silicon oi the medium, in addition to having a high specificgravity, is highly resistant to rust and is very hard and can beobtained at low cost. These characteristics make it unusually practicalior use of high specific gravity. Further, because of its magneticcharacter substantially all of it may be recovered so that it has along, useful life in the process and may be circulated many timesthrough the concentration tank. As a result of these features, thespecific gravity of the. medium in the concentration tank may becontrolled accurately at the predetermined high point required for theconcentration or the particular ore to be treated.

The ores which may be concentrated by my improved method require fluidmediums having specific gravities within the limits of about 2.5 to 3.3and for each ore the gravity oi the mediuin must be controlled within anarrow range. Ferro-silicons for use in forming the medium are availablehaving specific gravities varying from about 6.5 to 7.5, depending onthe porosity as well as the chemical composition.

The expression "iron composition as used in the appended claims, isintended to include ordinary and eutectic mixtures, alloys and compoundsof iron and steel where the iron constituent exceeds 75% by weight, ofthe composition.

In the claims the term "substantially self-sustaining" as applied to aseparating medium or liquid or fluid mass is intended to define gravityseparating media consisting of liquids such as water and comminutedsolids and supplied to a separating tank in such volume and at locity asto maintain the solid constituent thereof in suspension. I

Having described my invention, what I claim as new and desire to protectby Letters Patent is:

1. The method of concentrating an ore which consists in introducing itinto a substantially self-sustaining fluid mass consisting of comminutedparticles of an iron composition and a liquid, said compositioncontaining in excess of 75% by weight of iron, continuously floating thelighter constituents of the ore in said mass and allowing the heavierconstituents to settle therein, separately removing the heavier andlighter constituents oi the ore from said mass, washing the ironcomposition particles from the separated ore constituents, recoveringsaid composition particles from the wash water by magnetic attraction,whereby said particles become magnetized, then destroying the residualmagnetism of the recovered particles and returning said particles tosaid fluid mass.

2. The method of concentrating an ore which consists in introducing theore into a fluid mass consisting of term-silicon and a liquid, saidferro-silicon containing in excess oi 75% in concentrating oressuch ve-F by weight i or iron, continuously floating the tailings irom the orein said mass and allowing the ore concentrate to settle in said mass,removing the ore concentrates and a portion of said mass from the lowerpart of said mass, withdrawing the tailings and a portion of said massfrom the up r part of said mass, washing the ferro-silicon from theseparated ore concentrate and tailings, recovering the ierro-siliconfrom the wash water by magnetic attraction and returning theterrosilicon so recovered to said mass.

3. The method of concentrating iron ore and manganiferous iron orehaving a specific gravity in excess of 2.5 which consists in deliveringthe crude ore into a fluid mass consisting of ferrosilicon and water,the ferro-silicon containing approximately 82% by weight of iron and inexcess of 10% by weight or silicon, maintaining the specific gravity ofsaid mass at such point as to float the tailings trom'the ore and toallow the ore concentrate to settle therein and separately removing theore concentrate and tailings from said mass.

4. The method of concentrating an ore which consists in continuouslyintroducing the ore into a fluid mass of flotation medium consisting offinely divided ierro-silicon and water, continuously floating thetailings from the ore in said medium and allowing the ore concentrate tosettle therein, continuously removing the ore concentrate and a portionof said medium from the lower part of said mass, continuouslywithdrawing the tailings and a portion of said medium from the upperpart of said mass, continuously separating the bulk of the withdrawnmedium from the tailings and ore concentrate, returning the separatedmedium to said fluid mass, washing the ferro-silicon from the separatedore and tailings, recovering the ferro-silicon from the wash water bymagnetic attraction and returning the ferro-silicon so recovered to saidmass.

5. The method of concentrating an ore which consists in delivering thecrude ore into a substantially self-sustaining fluid mass consisting ofcomminuted particles of an iron composition and water, said compositioncontaining in excess of by weight of magnetic iron, maintaining thespecific gravity of said mass at such point as to float the tailingsfrom the ore and to allow the or concentrate to settle therein,separately removing the ore concentrates and tailings from the mass,washing said tailings and ore concentrates to remove adhering particlesof said iron composition therefrom, recovering said particles from thewash water by magnetic attraction whereby they become magnetized, thenconcentrating said particles by utilizing their residual magnetism toaccelerate their settling in water, then destroying residual magnetismof said particles and returning them to the fluid mass.

6. A process of concentrating ores which consists in introducing aflnely comminuted rustresistant ferro-silicon of magnetic susceptibilityinto a liquid to secure a liquid medium having a desired specificgravity, introducing said medium into a container, introducing the oreinto said medium, floating ore particles having less speciflc gravitythan that 0! the medium to the surface of the medium, removing saidlighter particles and some medium from the container and recovering saidcomminuted ferro-silicon from the removed medium by magnetic attraction.

'1. In a process for concentrating ore, the steps oi introducing the oreinto a gravity liquid flosilicon from the separated trateslandrecovering the i'e o-siiicon irom the tation medium consisting oi'-mlsnetlcallv a tive rust resistant ierro-silicon and water. thefe'rro-silieonhnd water mixed in proportions to form a liquid gravityseparating mediumhaving a specific gravity intermediatethe specificgravi ties of the ore particles to be separated, separating the oreconstituents in said medium. remov ing the separated constituentstogether with some of the medium, and then revering the term-siliconfrom said separated medium by magnetic attraction.

8. The method oi concentrating ores which consists in introducing theore into a fluid mam of flotation medium consisting oi finely dividedierro-silicon and water. continuously removing tailings and concentratesand a portion said medium from said fiuid mass, separating the bulk ofthe removed medium from the removed tailings and concentrates, returningthe separated medium to saidfiuid mass, washing the terroings and cencemwash water by magnetic attraction.

9. In a process of separating ore particles the 1 steps oiintroducingthe ore particles into a selfsustaining separating. medium comprising aliquid containing a comminuted rust resistant, abrasion resistant solidof magnetic susceptibility and wherein some or the ore particles sinkand some ore particles float, removing separated ore particles with someof said medium from the main body of medium, separating ore particlesfrom said removed medium, recovering by magnetic attraction comminutedmagnetic solid particles from the removed medium, whereby said solidparticles are magnetized, destroying the residual magnetism of saidmagnetized solid particles,,and then reusing the said particles in theseparating medium. i

10. The method oi cencentrating an ore having a specific gravity greaterthan 2.5, which consists in delivering the ore to a separatingtankcontaining-a substantially sell-sustaining fluid mass in whichtheheavier ore particles sink and the lighter ore particles float andconsisting of approximately 20% by weight oi water and a comminuted rustresistant iron composition in which composition the iron constituentexceeds 75% by weight, maintaining the specific gravity of the fiuidmass intermediate the specific gravity oi the ore particles to beseparated, recovering iron composition particles of used medium bymagnetic attraction whereby said particles become magnetized, settlingsaid magnetized iron composition particles in a suitable container, thenpassing the settled magnetized iron composition particles through analternating current demagnetizer whereby their residual magnetism isdestroyed, and then returning said recovered particles together withwater to the separating tank.

. 11. In a continuous process for separating ore constituents employinga liquid separating medium, the steps of subjecting the ore to a body 0!a substantially sell-sustainin liquid separating medium containing afinely divided rust-resistant metal or magnetic susceptibility andwherein some oithe ore particles float and some sink, removing theseparated ore particles and some medium from the main body oi medium.

, recovering finely divided metal particles of the removed medium bymagnetic attraction whereby said comminuted metal particles becomemagnetised, destroying the residual magnetism of said magnetized metalparticles by passing the same through an alternating currentdemagnetiser, and then returning said demagnetized particles to theseparat ng medium.

12. A process of concentrating ores which consists in introducing afinely 'comminuted rustresistant iron alloy having magneticsusceptibility into a liquid sustaining liquid medium having a desiredspecific gravity, introducing said medium into a container, introducingthe ore into said medium; floating ore particles having less specificgravity than that of the medium to the surface of the medium, removingsaid lighter pairticles and some'medium from the container, recoveringby magnetic attraction alloy particles contained in the removed mediumwhereby said alloy particles become magnetized, destroying the residualmagnetism of said removed alloy particles, and then returning therecovered particles to the separating medium while maintaining theself-sustaining character of said medium. I

13. In a process of separating ore particles, the steps of introducingthe ore particles into a substantially self-sustaining separating mediumcomprising a liquid containing a comminuted solid of magneticsusceptibility suspended therein, said medium being of such specificgravity that some of the ore particles sink and some ore particles fioattherein, removing separated ore particles with some 01' said medium fromthe main body of medium, separating ore particles from said removedmedium, recovering by magnetic attraction comminuted solid particles ofmagnetic susceptibility contained in the removed medium whereby saidsolid particles are magnetized, destroying the residual magnetism ofsaid magnetized solid particles and then reincorporating saiddemagnetized solid particles as HENRY H. WADE.

to secure a substantially selt-,

